1. Field of the Invention
The present invention relates to a device for changing the direction of an airstream in, for example, a wind tunnel used for testing aerodynamic designs.
2. Description of the Related Art
When a vehicle is running it is often affected by the impact of a cross wind, i.e., the direction of the force of the airstream on the vehicle body is abruptly changed, and this causes an abrupt change in the various forces of the airstream acting on the vehicle body and this abrupt change affects the running stability of the vehicle. If the various forces caused by a change in the direction of the wind acting on the vehicle body can be detected, it becomes possible to estimate the running stability of the vehicle when the vehicle encounters a cross wind, and thereby obtain useful data for the design of a vehicle.
From the viewpoint of safety, however, as well as the difficulties in obtaining a stable detecting condition, it is difficult to obtain such data when the vehicle is actually running, and therefore, such data is normally obtained by using a wind tunnel in which a state in which the vehicle encounters a cross wind when running can be artificially created, i.e., simulated.
In a known airstream generating device by which the direction of the airstream can be changed, a plurality of spaced airstream direction control plates having a wing shape are arranged in a wind tunnel such that these plates are swingable about the central axes thereof while maintaining a parallel relationship therebetween. (See Japanese Unexamined Patent Publication No. 61-110024.) In this airstream generating device, the airstream direction control plates are periodically swung about the central axes thereof by step motors, to artificially created an airstream from different directions, similar to the air currents in the atmosphere, to observe the behavior of the smoke, discharged from, for example, a factory chimney.
Nevertheless, the movement of air currents in the atmosphere is quite different from the movement of an airstream to which the vehicle is subject when running, and thus, even if this airstream generating device is applied to a device for testing the running stability of the vehicle, it is impossible to artificially create a state simulating the conditions encountered by a vehicle when subjected to a cross wind while running.